Method and apparatus for brazing cylindrical stock



C. N. HUNTLEY ET AL June 19, 1951 METHOD AND APPARATUS FOR BRAZING CYLINDRICAL STO 3 Sheets-Sheet 2 Filed Dec. 31, 1947 lww Jun 1951 c. N. HUNTLEY ET AL 2,557,745

METHOD AND APPARATUS FOR BRAZING CYLINDRICAL STOCK Filed Dec. 31, 1947 3 Sheets-Sheet 3 F g 7. 7/ 7/ j 9/ 72 To TevrninaLs 64 and 65.

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large number of finished Patented June 19, 1951 v UNITED METHOD AND APPARA CYLINDRIC Charles N. Huntley,

TUS FOR BRAZING AL STOCK Cleveland Heights,

and Clarence E. McKinsey, Painesville, Ohio, assignors to General Electric Company, a corporation of New York Application December 31, 1947, Serial N 0. 794,930

6 Claims. Cl. 21910) Our invention relates and The above described defects, unless obviated by expensive manufacturing procedures which of core-rod which is subsequently drawn down by means of dies, to form lead-in conductors for electric lamps and electric discharge devices, such non-uniformities will result in a large number of defective finished products, since a defect in a large diameter rod will be evidenced in a very lead-in Wires of a diameter and length suitable for use in electric lamps, radio tubes, discharge devices, etc.

Furthermore, previous brazing methods wherein the core-rod, or copper tubing, is brazed by a gas furnace, have entailed a further the very tenaciously adherent oxide which is formed on the rod during The oxide coating is very hard, making it necessary to repair frequently the dies through which the rod or tubing is subsequently drawn.

It is an object of our invention to provide new and improved methods of brazing or welding stock material comprising an inner core member and an outer metallic tube or sleeve.

It is another object of our invention to provide a new and improved machine for brazing cylindrical or tubular stock.

Generally speaking, in accordance with our invention we provide methods and apparatus for welding, brazing and joining cylindrical stock such as core-rod including an inner metallic core, an outer copper tube or sleeve, and having a layer of a flux between the core and the tube. The stock is passed through a high frequency magnetic field for heating the core and sleeve and particularly for melting the flux to obtain a unialthough the utilization of our limited thereto,

having a frequency such that the depth of penetration of the induced secondary currents extends at least to the region or vicinity of the flux, and preferably penetrates just to and slightly beyond the inner boundary of the flux. We provide rotational movement to the stock as it moves through the high frequency magnetic field so that when the flux flows or is melted there is maintained an even annular distribution of the flux between the core and the outer tube. In this way we assure that upon cooling there is a uniform annular union or bond between the core and the tube, which bond is also uniform throughout the entire length of the core-rod.

We also provide a new and improved machine whereby continuous brazing of tubular stock is obtained, and whereby tubular stock can be continuously supplied to the machine and automatically unloaded, there being no need for interruptions in the manufacturing process.

For a better understanding of our invention reference may be had to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. Figs. 1 and 2 are front elevation and plan views, respectively, of a machine for carrying out the above described process, and which includes means for heating by high frequency induction core-rod and similar stock, whereby the stock is translated through a heating coil and rotated to obtain the desired welding or brazing of component parts of the stock. Figs. 3 and 4 are cross-sectional views of the high frequency heating coil through which the stock is moved.

Fig. 5 is a detail view of one of the driving heads, and Fig. 6 is a detail View of the Watercooled driving head immediately to the left of the heating coil as viewed in either Figs. 1 and 2. Fig. 7 is a diagrammatic representation of the electric circuit for controlling the energization of the high frequency heating coil.

According to our method of welding or brazing core-rod, or other cylindrical stock such as metal-clad cable, etc., we employ a high frequency magnetic field the frequency of which is correlated to the depth of penetration required in order to produce the desired union or bond between the component parts of the stock. The depth d of penetration of the induced or secondary currents in the stock may be expressed as:

d=depth of penetration in inches p=resistivity of the material, microhm-cm. a=permeability j=frequency in cycles per second Where the component parts of the stock are .so that the melted flux is uniformly distributed as of the same material, the above expression may explained above. Each of these rollers includes be employed to determine for a particular freopposed beveled or truncated conical surfaces quency the depth of penetration of the induced forming a cradle to hold the core-rod, and a currents. In those instances where the comtensioning wheel 23 engages the core-rod 2 from ponent parts of the stockheing processed are above. The wheel23 exerts a downward force different, such as magnetic and non-magnetic on the rod, thereby increasing the fritcicnal enmaterials, the above expression may be used-with gagement between roller 22 and the rod.

a reasonable degree of accuracy toobtain a rough Each driving head includes an angularly posiestimate of the depth of enetration. l0 tionable frame 24, supported from the bearing Furthermore, in carrying out our method we shaft I! and holds a vertical electrical insulatcause rotation of the cylindrical stock during the n p St25 c ry a b t 26 which pos tions heating process in order that the melted flux is and holds shaft 21 on which driving roller 22 and uniformly distributed annularly. Of course, the the sprocket aremounted. Tensioning wheel speed or lineal motion or translation through the 15 23, which may be knurled, is supported from the high frequency field is related to the particular bracket by a pivoted arm 28, and :is biased material .or stock being brazed so that the flux is downwardly by an adjustable tension spring 2! properly melted, and speed of rotation is also supported by the bracket 26. Bracket-25 isangudetermined in order to obtain even annular dislarly adjustable or rotatable by virtue of the tribution to assurea uniform bond when the stock 0 collar thereof which eng Po and is cooled .or cooling after removal from the magserves as a means for adjusting the axis of rota- ,netic field. tion of roller 22 with respect to the longitudinal Referring now to Figs. ,1 and .2, which are,,reaxis of the rod. In this manner, we provide .spectively, front elevation and plan views, we means l Co tr ing and adjusting the number provide an apparatus for continuously brazing 25 of revolutions the rod is rotated per unit of ionor welding core-rod, having magnetic or nongitudinal or translational movement imparted to magnetic cores, as an example of which referthe rod. As the axis of rotation of the roller '22 once may be 'had to the above described core-rod r ve to the '06. XiS S h n Om & having a copper sleeve and a core of a magnetic degree position to smaller or oblique angles, the material such as a nickel-iron alloy. The ma- 30 number of revolutions, or th revolvin ot chine there shown comprises a high frequency isv increased. Adjustable tenSiO p 29a r heating coil l for welding or brazing core-rod sprin 29 rv a a m ns r v yin the 2+5 which is shown as being ,in suitable lengths te s oning force applied to rods of different of about four to six feet for ease in handling. diameter and surface characteristics to assure The coil 1 and the driving and energizing equipuniform, synchronous and continuous rotation of ment may be housed in and supported by a the rods. The plane of rotation of the wheel frame 6 having a front or panel section 1, a 23, is parallel to or substantially parallel to the table 8, and a set-back upper panel 9. plane of rotation of the rod at the point of con- As a means for moving the core-rod through t ct o t e d nd e W e l 3 the high frequency heating coil 1, we provide a Dr ve sh ft 8. s i t driven by a y m plurality of conveying or driving heads 10-46, of chains and sprockets from a suitable electric which are positioned to engage the core-rod and m t through an adjustable Speed r u move it to the left, through the heating coil, and driv 33. a n a p d ad us n 3 A st rt ultimately to an unloading position or station. and Stop sw tch 35 may be provided to Permit The spacing of the driving heads is correlated separate and independent control of the driving of course, to the length of the stock being y processed, and the position of the heads may be 6 ShOWS in some detail e Water-cooled adjusted by movement along a supporting rod driving head It in cross-section in theplane c-.c. or'bearing rod 11. The driving heads Hi-[ 5 are In h s fi ur l m n s rr sp nd n to thos similar in construtcion and arrangement. Howh wn n Fi 5 have been assigned like referenc ever, driving head I4, is provided with a wat rnumerals. However, it will be noted that a cooling channel because of its position immebeveled driving ro l 3615 p v d d With-a hollow diate'the output side of the coil 1. Fig. 5 shows s t 31 rv n as a ool ng conduit, the shaft the construction of driving head 15 as iewed being pp from a cooling water system infrom the lane d,-d,, while Fig, 6 sh s th eluding conduits 38 and 39 and suitable waterstruction of driving head I l. The driving heads tight bushings 49 and M to permit the necessary 10-416 are all driven from a single drive shaft relative rotation between the stationary conduits 18 through individual chain and sprocket ar- 38 and 39 and the rotating shaft 31. This driving rangements. roller 36 may be additionally supported by a The :driving heads 10-46 which we provide, further bracket arm 42 supp y 1 st and which are described hereinafter, serve t Figs. 3 and 4 show in detail features of the high impart to the rod rotational movement in addifrequency heating coil l. Of course,-the design-of tion to the longitudinal or translational movethe coil I will depend upo the particular ap inent. Furthermore, each of these driving heads tion, that is, the nature of the stock to be welded ,is adjustable so that the amount of rotational 55 or brazed. The interval of time that the stock is .movement with respect to the longitudinal movemaintained within the coil is furthermore a funcment is controllable or adjustable. tion of the field strength, the thermal conductivi- Referring to Fig. 5, each of the heads [EL-l3, ty an h mal pa y of the k- These and I5 and It, comprises asprocket I9 mounted factors determine the lineal speed at which the on shaft ill, a driven sprocket gear 20 and an stock is moved through the coil or region of ininter-connecting link belt type chain 2|. We duction heating. The speed of rotation is doprovide in each of the driving heads a roller .22 rm by the e Of rotation q r to mainwhich not .only :moves the rod along its intended tain an even distribution of the melted flux. translational course, but also imparts to it a For core-rod stock of about 0.45 inch diameter rotational movement'a-bout its longitudinal .axis we have found that a coil I having 61 turns,

ing varnish or closely spaced, may be employed. The conductor 43 constituting the coil I is hollow in order to permit cooling thereof, and may be square copper tubing having an outside dimension of inch, and an inside dimension of inch, as shown in Fig. 3 which is a cross-sectional view of the coil I in zone a-a. The square copper tubing is insulated by suitable refractory insulation such as Plexiglas tubing, or fibre 44, dipped in insulatcompound and baked for hardening. Such a coil was wound to have an inside diameter of 7 inch and an outside diameter of 1% inch. The overall length of the coil I was 17% inches. The core-rod was driven through the coil I at the rate of 24 inches per minute, and the rod was rotated one revoution per inch of linear travel.

As shown in Fig. 4, which is a cross-section view of the coil I through the plane bb, the core-rod 3 is spaced from and centered in th conductor 43 as it is moved through the coil I. The coil I is supported by a refractory ceramic frame 45, held above the table 8 by four thermal and electrical insulating posts, only two of which, 46 and 41, are shown in Fig. 1.

The rod is, of course, placed in the machine at the right hand Side and the rod is moved through the coil I to the left to the unloading position where there is an inclined unloading table 48, supported by brackets from bearing shaft I1, and having positioned thereon a plurality of retarding arms 495|, the last of which is shown in Fig. 5. One end of the retarding arm which is representative of the others also, is supported from the underside of the unloading table, and is provided with a loop section through which the rod passes while held and engaged by driving heads l5 and I6. The other end of the unloading arm is formed to conform to the surface and plane of the unloading table and is spring biased toward the table surface and engages it.

In order to unload the brazed rod, we provide unloading arms 52 and 53, the latter of which is shown in Fig. 5. These arms are actuated automatically in response to finished core-rod position, and are mounted on a shaft 54 which is rotated by an electro-magnet 55 and lever-arm 53a, the magnet 55 being controlled by either switch 56 or manually operated switch 51. Switch 56 is positioned to be. engaged by the end of each processed core-rod when it reaches the end of its travel. Upon actuation of switch 56, arms 52 and 53 are rotated by shaft 54, and strike the finished rod. Due to this impact the rod is moved onto the table 48 and rolls along it to be engaged and retarded by arms 49, 50 and 5|, but which however permit the rod to drop. The finished rods 58 are thereby unloaded and rolled into a truck or other vehicle positioned below the unloading table 48.

We have found that it is important to maintain a constant rate of cooling of the coil I in order to to perform satisfactorily the welding or brazing operations by maintaining the coil resistance constant. We provide means for circulating cooling water through the hollow conductor 43 of coil I at contsant pressure, preferably at 60 pounds per square inch pressure for the above described coil dimensions, and transmit through the cooling system about five pints per minute. For this purpose we provide a motor 59, a pump 60, an adjustable pressure regulator 6|, and a reservoir Ma. The conduit 62 is connected to the input side of the water cooling system for the coil, and a discharge conduit 63 i provided for the cooling water. Cooling water is supplied to driving head I4 through conduits 38 and 39.

High frequency electricalconnections to the coil I are made through terminals 64 and 65. We employ a particular electrical system for energizing the coil to maintain the energization of the coil constant, and to assure thereby uniform bond between the core and the sleeve. A high frequency generator 66 having an armature winding 61 and a field winding 68 supplies high frequency alternating current to coil I through circuit 69. Generator 66 i driven by a motor 10, which may be a three phase induction motor, energized from a three phase supply circuit 1| through a starter 72.

We employ an exciter I3, which may be of the armature-reaction-excited or amplidyne type having a pair Of direct current output brushes I4 and 15 connected to the field winding 68 through a fuse 16. A pair of short-circuited brushes I1 and 73 are connected as shown. Field winding 19 supplies the principal separate excitation for the exciter l3 and is energized from a source of constant voltage direct current 80. In order to control the excitation of exciter 13 and hence the excitation of generator 66 to maintain the output voltage thereof constant, we provide a unidirectional component of voltage which varies directly as the magnitude of the alternating high frequency voltage supplied to coil I through circuit 69. This means may include a selenium rectifier 93 and an output adjusting voltage divider 8| having an adjustable contact 62 to provide a direct current component of voltage which opposes a component of the constant voltage source derived from a voltage divider 83. Further adjustable means, such as a rheostat 84 may be connected in series with the rectifier 93 to control the voltage which is supplied to circuit 69 and coil I. Additional rheostats or variable resistances 85 and 86 may be connected in series with rheostat 83 to control the amount of current supplied to winding I9. Field winding 8! of exciter 13 may be used as an anti-hunt winding and is connected in series with parallel-connected capacitances 88 and 89 and is energized in response to transient voltage variations of the direct current output voltage of exciter 13. The exciter 13 is driven by a, three phase induction motor 96 which may be energized from circuit 7| through a switch 9| and fuses 92.

Since the resistance of the coil I is maintained constant during operation by the constant rate of cooling thereof, it will be appreciated that the above-described circuit maintains constant the power supplied to the coil.

Of course, various arrangements may be used to render the machine readily adaptable to high production systems. For example, an electrical counter and indicator system as shown in Fig. 1 may be used to furnish a running and continuous count of the number of rods processed. The electrical counter may be connected in the electrical circuit of switch 56 to actuate the counter automatically. In addition the counter may be provided with an integrating means to energize a signal, such as a lamp, when the number of rods processed attains a set value.

One of the principal advantages attained by the use of our above described method and apparatus is the very substantial reduction in the amount of oxide which is formed on each rod during the high frequency brazing thereof, as contrasted with that formed when the rod is brazed in-a j gas furnace.

rzysewms In" the base of: copper :rod brazen by high-frequency, there is much less oxide formed, and this advantage "is further enhanced-by the radical difference in the nature of theoxide, whichis-readily removed by mild imwpact-or mild rubbing, which-is a very marked advantage because much less frequent repair of the ":diesemployed in the subsequent drawing opera- 'tions is required. ;If desired, a separate hydrogen "burner (not shown) may be used to deoxidize the :rodzas'it emerges from the coil I, thereby ren- :dering the stock completely free of oxide coating.

In brazing-a core-rod stock comprising an ingner magnetic core and an outer sheath or copper fitubehaving therebetween a sheath or layer of brass brazing flux, we have found that where the ".over-all outside'dimension is about ;45 inch, and the copper tube isabout 35 mils thick, that very satisfactory welding or brazing is obtained be .tween the core and the tube by using a magnetic r field-having a frequency of 9600 cycle per sec- --ond, the interval of time that the stock is main- -tained within the magnetic field depending, of course, on the Strength of the field, which of course, is determinative of the rate of movement of the stock through the field. In such instances, the brass flux may be about '70 per centzinc -and 30'per cent copper, having a thickness of about 2 to 3 mils, and wound in strip form about the-core prior to placing it in the outer copper sleeve or tube. Under such conditions, and using a-highfrequency current of 67 amps., we have found that magnetic core-rod of the stated di- -mensions may be very satisfactorily brazed by movingthe rod through the coil l at the rate of .24 inches per minute and by imparting to the rod a rotational movement of one revolution per inch wof linear traveL'that is, the rod is rotated at 24 RP. M. For the stated conditions, the amount 0f .powersupplied to the coil! was 13.5 kw.

.For a magnetic core-rod of the above stated dimensions and using a frequency of 9600 cycles .per second, the secondary or induced currentsdo not, ofcourse, penetrate to the region of the brass flux, inasmuch as it will be appreciated that the presence of the magnetic core serves to limit the depth. of penetration of the currents to a value .less'than that established by the above equation. ,.However, due to the high thermal conductivity of the copperconstituting the sheath, the heat ..prod,uc,e'd.by the induction quickly flows to the 'lower melting point flux to melt it. as is desired.

What weclaim as new and desire to secure bygLetters Patent of the United States is:

.1. The method of brazing cylindrical stock, -includinga magnetic core, a. copper sheath completely enclosing said core and a flux therebetween, which comprises passing the stock throughan alternating magnetic field of a frequency to produce an appreciable depth of penetration. of the induced currents into said sheath, and rotating the stock to maintain an even dis- .tribution ,of the melted flux.

;2. The method of brazing core-rod, including ,a core comprising an iron alloy, a copper sleeve completely enclosingsaid core and an inter- ,spaced tube of a brazingflux, which comprises .passing [the rod through an alternating magnetic field to produce a depth of penetration of the induced currents suflicient for melting the *flux, and rotating said rod to maintain an even annular distribution of the flux.

.13. The methodof brazing core-rod, including -a;eo're "including iron, a copper sleeve completely enclosingsaid core and an interspaced'tube of. a

brazing flux, which comprises passing the through an alternating high frequency'magnetic field of a'frequency such that the induced '-currents in said rod penetrate toward the region of the flux to melt the flux,'and rotating-said rod to maintain an even annular distribution of 4. ,The method of brazing cylindrical stock comprising a magnetic core, a'copper outer'tube ciable penetration of the secondarycurrents into said tube while continuously rotating saidstock to maintain an even annulardistribution-of the meltedfiux between the tube and the core, and subsequently drawing the stock down to wire of relatively fine I diameter.

"5.The method of brazing core rod of about .45 inchdiameter and including a core'comprising iron, a copper sleeve about35 mils thick and an intervening layer of metallic brazing flux, which method comprises rotatingthe rod about its axis'at a rate of about 24 R. P. M. and passing it linearly at'a speed'of about 24 inchesper minute through an alternating magnetic field having a frequency of about 9600 cycles per second anda power supplied thereto of about 13.5 kw.

6. In a machine for brazing cylindrical stock including an inner metallic corezand an-outer -metallic tube with an intervening layer of flux of about 13.5 kw means for circulating cooling water through said coil at constant pressure, and drive'means constructed and arranged'to'move said stock-linearly through the interior of said coil at a speed of about 24 inches per minute while rotating said stock about its axis at a rate of about one'revolution per inch of lineartravel.

'CHARLES N. HUNTLEY.

CLARENCE M0KINSEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Babat, Construction of Heating Coils for Induction Surface Hardening, in Heat Treating andForging, Jan. 1941, page 39. 

